Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2010
Publication Date: 7/1/2010
Citation: Burke, J.M., Coleman, S.W., Chase, C.C., Riley, D.G., Looper, M.L., Brown, M.A. 2010. Interaction of breed-type and endophyte-infected tall fescue on milk production and quality in beef cattle. Journal of Animal Science. 88:2802-2811. Interpretive Summary: Calf growth is often reduced in response to decreased milk production in cow-calf production utilizing endophyte-infected tall fescue and costs the beef industry millions of dollars annually. Use of a tropically adapted Bos taurus beef breed, Romosinuano, that is more thermo-tolerant may allow for a tolerance to fescue toxins and improve calf production on tall fescue. Scientists from USDA, ARS Booneville, AR and Brooksville, FL determined that milk production was similar between Angus and Romosinuano cows, but milk quality traits differed; and while Romosinuano cows showed no signs of heat stress when grazing tall fescue during summer months, signs of fescue toxicosis still existed. These results provide information on potential genetics for cow-calf production on endophyte-infected tall fescue, information that is important to producers, extension agents, and scientists.
Technical Abstract: Milk production of beef cattle grazing endophyte-infected (EI) tall fescue (TF) (Festuca arundinacea), an important cool season grass in the southeastern U.S., is often decreased and can impact calf growth. The objective of this study was to determine whether a thermo-tolerant Bos taurus breed of cattle, Romosinuano (RO), would tolerate EI TF toxins relative to Angus (AN) cattle. Milk production and quality were examined on 73 AN and RO cows grazing endophyte-free (EF; ‘K-31’) or EI TF (‘K-31’) along with growth of their calves in 2007 and 2008 in west central Arkansas. Cows calved between early February and late March (spring) and milk yield and quality was determined by way of milking machine starting on d 57.1 plus or minus 2.6 post-partum and every 28 d thereafter between April and August. Body weight of cows and their calves sired by a Charolais, cow rectal temperature and serum concentrations of prolactin were also determined. Forage type did not influence milk yield, but this trait was greater in AN compared with RO cows (P less than 0.001). Percent milk fat was greater in cows grazing EF TF in April, but greater for cows grazing EI TF in July (forage × month, P less than 0.001) and greater for RO than AN cows (P less than 0.001). Percent milk protein (P less than 0.001) was greater and somatic cell counts (log transformed; P less than 0.001) less in RO than AN cows. Percent milk lactose was greater for RO compared with AN cows in June through August (breed × month, P less than 0.005). Body weights of calves were generally the same across forage and breeds between April and August 2007, but were less in calves raised by RO cows grazing EI TF than others in May and June 2008 (forage × breed × month × year, P less than 0.003). Rectal temperature was similar between RO cows grazing EF and EI TF, but greater in AN cows grazing EI compared with EF TF in most months (forage × breed × month × year, P less than 0.001). Serum concentrations of prolactin were reduced in both breeds of cows grazing EI TF between April and July of both years and greatest in RO cows grazing EF TF (breed, P less than 0.001; forage × month, P less than 0.001). These data suggest that RO cows were more thermo-tolerant, but still susceptible to toxins in EI TF as shown by a reduction in serum concentrations of prolactin. However, milk production was not influenced by EI TF as previously observed, but milk fat percent was decreased in April in this group of cows. Milk yield and quality was different between AN and RO cows during the period of lactation observed.